Prescription Tires Buying
a car with odd tires sizes or expensive performance tires can be a
costly mistake when it comes time to re-shod your vehicle.
As I noted in my
Prescription Motor Oil
posting, buying a car which requires special motor oil that costs $10 a
quart gets to be real old, real fast. When the number of places you
can take your car to get the oil changed is limited, then you have to
pay through the nose for something as simple as an oil change.
My next car will burn regular gas and use regular oil, and if they don't
carry the oil filters at Wal-Mart, well, I ain't buying the car,
period. While having esoteric cars is fun and all, they can easily
double, triple, or quadruple the cost of car ownership.
And nowhere is this more true than with tires. In the old days, tires
came in three sizes - 13", 14" and 15", and most gas stations stocked
the right tire for your car - there were maybe a dozen sizes in all.
Today, tire sizes are all over the map, and not only that, they are
changing with time. What was a popular tire size 5 years ago is hard to
find today.
As this report notes
,
the most popular OE (Original Equipment) sizes today are far different
from what are the most popular replacement sizes being sold (which
represents the older cars on the road). This is a nightmare for tire
dealers, as they have to stock an even wider array of tires in multiple
sizes.
As the report shows, the trend is toward larger sizes, with 16" and 17"
inch sizes being the norm today, and older sizes such as 13" and 14"
being nearly non-existent, while 15" is fading fast.
In addition to rim diameter, there are other aspects of tire size - the
width and aspect ratio. In tire size parlance, as size such as P225/60
R16 has three numbers - 225 representing the width, 60 the aspect ratio
(width to height) and 16 being the rim diameter in inches. Some sizes
are very popular, others, usually performance sizes, quite rare. And it
is possible to alter aspect ratio and width somewhat on some cars,
although changing sizes beyond what manufacturers spec can be
problematic.
In the olden days, you might find your car shod with P235/75 R15 tires,
which were fairly "tall" tires (aspect ratio of 75%). But today,
"series 60" and below are more common - tires that in the 1960's would
have been considered "ultra low profile" tires. So the general trend
is toward larger diameters and lower profile tires across the car
lines. The bulbous balloon tires of days gone by are fading fast.
HR78R15's are nowhere to be found these days.
But beyond the switch in rim sizes, there are other considerations that
are more relevant. In particular, there is the phenomenon of the
"unintended performance tire customer". Today, most cars are sold with
alloy wheels and lower profile tires. Many people buy cars with these
sort of rim/tire combinations without thinking about them too much,
other than maybe the rims "look pretty".
But when it comes time to re-shod the car, they are shocked to find out
that these tires cost $250 apiece and more, particularly if they are an
esoteric size that is hard to find.
For a performance-oriented driver, perhaps this excess cost might be
justified - although as someone with two "performance" cars, I am not
sure that even this is the case. In our modern world, there are few
places where you can safely drive a high-performance car to its limits,
and below those limits, there is little need for extreme rubber on your
wheels. Moreover, the sacrifice in ride quality and tire life (in
particular) is questionable, if the only benefit is that once in a great
while, you can take an off-ramp at 1.0 g.
Thus, for example, I am looking for replacement tires for my X5. These
are Michelin MXV-4 "Energy" tires, which are hardly an esoteric
high-performance model. They are, however, low profile P255/55 R18
sized, which is an oddball size to find. These were the "upgraded"
tires which came as part of the "Sport Package" as opposed to the more
plebian (and easier to find) 17" stock rubber. Most tire stores stock
15", 16" and 17" sizes. Few stock many 18" tires, and fewer still the
low-profile P255/55 series.
The Michelins are good-wearing tires, with over 60,000 miles on them so
far (which is their warranted service life) but to replace them will
cost $250 apiece plus mounting and balancing, which is a lot of money
($1000+) for a car worth maybe $10,000 on a good day. Most likely, they
will be a special-order item, perhaps from the tire rack.
The M Roadster definitely has prescription tires P225/45 R17 in the
front and P245/40 R17 in the rear ( a so-called "staggered" arrangement
which makes rotating tires out of the question). While these are 17"
sized tires, which is a popular rim diameter, they are a fairly rare
performance aspect ratio and width. These tires ride very harshly and
barely cover the rims, which tend to rash as a result. Like many folks,
I decided to go up one size and change the stock 225/45/17 on the front
to 235/45/17 and the stock 245/40/17 on the back to 255/40/17.
The original tires lasted less than
30,000 miles, which is not unusual for a high-performance tire with a
soft compound. And therein lies another problem with high performance
tires - they don't have much of a treadlife. And ironically, many of
these "high performance" tires are dodgy in the rain, and of course
useless in snow or other hazardous conditions.
I
decided to go with Bridgestone Potenzas, which were more of a passenger
car tire than a racing tire, and they have a very good service life. I
got a deal on these at a silent auction for about $200 the set (!!).
Otherwise, they would have cost over $1200 easily, if I went with a
"performance tire" replacement.
So
what do we learn from this? When shopping for a car, new or used,
consider tire sizes carefully. If you want reliable, basic
transportation, it doesn't pay to have a car that requires prescription
motor oil, premium gas, or special odd-ball tires.
Performance or odd-sized tires often have the following problems:
1. Short tread life (30,000 miles or less) which means replacing tires more often and paying more often for mounting and balancing.
2. Odd sizes, which means special ordering, which means little or no discounts, high tire prices, and little likelihood that such tires will ever be "on sale" at your local store.
3. Poor performance in the real world - racing tires often have poor rain and snow performance and ride harshly and allow for rim damage.
4. Leaving you stuck: If you have a car with esoteric tire sizes and have a blowout on a Sunday night, chances are, you'll have to get a motel room and your car towed in, as it may take days to order the special replacement tire and have it mounted. Many high-performance cars have no spares.
Having
a high performance car is fun and all, but when you get older and
realize that the amount of money you will earn is a finite amount - and
that you'd rather be doing things than owning things, the idea of having fancy tires which are of little real advantage in the real world, well, it gets old real fast.
If
you just want basic transportation and the optimal cost/benefit ratio,
buy a car with fairly standard sized tires and wheels - tires and wheels
that are readily available and that can be replaced cheaply when the
time comes.
Because, when it comes down to it, what you do
with your car is more important than what options it has. And if you
can't afford to go on vacation this year because you had to spend $1000
on tires that last only 30,000 miles, well, you have to ask yourself if
it was worth it.
And of course, the idea that every car needs to
have alloy rims is sort of silly as well, but I will address that in
another posting. Steel wheels might not be sexy, but they are cheap and
durable.
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